Nest temperature sensor "can't connect"

[GunxGuy]

I just installed a Nest Learning Thermostat and it seems to be working. I am trying to add a Nest Temperature sensor to the setup. I added it to the home app with no problem. However when I "Check connection" to the sensor it says "your thermostat is looking for your sensor" and then after a minute or so I get "Can't connect to upstairs thermostat. Find a spot closer to your thermostat and try again." The sensor is less than ten linear feet from the thermostat with no meaningful obstructions. There is a nice strong wifi signal there. As you can see in the image below, the remote sensor shows as a ? in the nest app. Any idea what is going on? Thanks!

[GunxGuy]

After more digging, found the answer, here. Worked perfectly!

https://www.reddit.com/r/Nest/comments/hniald/nest_temp_sensors_offline/hmhu0fo/?context=3

[morttt]

This worked perfectly, thanks for the link

[dchoule01]

I read all the replies and tried everything except fully resetting the hallway thermostat, I didn't feel like putting all those settings back in.  I did find something that worked though... I removed the battery from the sensor and removed the sensor from the phone app.  In the phone app I added a new product, selected sensor, scanned the QC code, it added to my account successfully.  The next step in adding the new product is to have the thermostat find the sensor.  When the app says to pull out the plastic battery tab to "wake up the sensor" that's when you put the new battery in the sensor.  Not sure but I think there's a time limit as to how long the sensor will broadcast, if you put the battery in too soon it will eventually go quiet and the thermostat can't find it.  At least that was the case for me, when I left the battery in for a while and later tried to have the thermostat find it, it couldn't.  When I put the battery into the sensor right when it told me to pull out the plastic tab, it worked within seconds the first time.